Color-television system



Dec. 11, 1956 D. RlcHMAN COLOR-TELEVISION SYSTEM 4 Sheets-Sheet 1Original Filed Dec. 18. 1951 ATTO R NEY Dec. 11, 1956 D. RICHMAN2,773,930

COLOR-TELEVISION SYSTEM Original Filed Dec. 18, 1951 4 Sheets-Sheet 2 D.RICHMAN COLOR-TELEVISION SYSTEM Dec. l1, 1956 4 Sheets-Sheet 3 OriginalFiled Dec. 18, 1951 ATTORNEY 4 Sheets-Sheet 4 DONALD RICHMAN Bw JATTORNEY/ Dec,l1, 1956 D. RxcHMAN COLOR-TELEVISION SYSTEM Original FiledDec. 18, 195i` United States Patent O CoLoRnrnLEvrsroN SYSTEMContinuation of application Serial No. 262,308, Dece v ber 18, 1951.No.426,968

27 Claims. (Cl. 1785.4)

This application May 3, 1954, Serial General The present inventionrelates in general to color-television systems, especially to suchsystems compatible with monochrome systems embodying the currentstandards in the United States and, in particular, to new and improvedsignal-translating apparatus for use in color-television receivers ofsuch systems. More specically, the invention relates to such apparatuswhich has the characteristic of reducing the annoyance to the viewer ofa reproduced image, of random brightness noise uctuations developedtherein and caused by the presence of undesired color signals. Thepresent invention lis related to that described in the copendingapplication of Bernard D. Loughlin, Serial No. 159,212, led on May l,1950, and entitled Color-Television System and is a continuation ofapplication Serial No. 262,308, filed December 18, 1951, and entitledColor-Television System, whichy is now abandoned.

In one form of compatible television system, more fully described in theRCA Review for December 19'49, volume X, pages S04-524, signalsrepresentative of the primary colors of the image being televised aresampled at the transmitter by a device having symmetrical electricalcharacteristics with respect to these color signals, thereby utilizingapproximately the same amount of signal energy for green, red and bluecolor signals of similar color intensities. The sampling processdevelops a composite color signal having a color subcarrier wave signalof a frequency of approximately 3.6 megacycles which has arnplitude andphase characteristics related to three different color-signalcharacteristics, being modulated in succession at 120 intervals by thelow-frequency components of those color signals. In addition, amonochrome or brightness component is developed from the primary colorsignals which is composed of equal energy values of green, red and blueand conventionally has a band width of -4 megacycles. The combination ofthis monochrome component and composite color-signal component producesa composite video-frequency Ksignal having a band width of 0-4megacycles, which modulates a Wave signal and is transmitted.

The modulated wave signal is intercepted by a receiver and a synchronousdetector, similar to the sampler described above, is utilized at thereceiver selectively to detect the low-frequency components of the colorsignals from the composite video-frequency signal at 120 intervals of acycle of the color subcarrier wavesignal. These derived color-signalcomponents are then :combined with the high-frequency components of thereceived monochrome signal electively to provide three color signalseach having a band width of 0-4 megacycles for application to thecontrol circuit of the image-reproducing device.

ln such a symmetrical sampling system, thederived color signals .aredeveloped from a composite color signal which simultaneously occupiesthe same frequency band in the system as the high-frequency monochromecomponents. Due to many reasons including extraneous noise 2,773,930Patented Dec. 11, 1956 developed in the band through which the colorsignals are translated and due to cross talk between the highfrequencymonochrome components and the compositel color signal, the derived colorsignals may include undesired noise-signal components which tend tocause spurious color signals to appear in the reproduced image. Forexample, high-frequency random-noise signal components havingfrequencies above 2 megacycles but below the upper frequency limit ofthe video-frequency signal band, when heterodyned with the 3.6 megacyclesubcarrier wave produce low-frequency noise components in the 0 2megacycle band occupied by the color-signal components. Theseheterodyned noise-signal components are in addition to the usual randomlow-frequency noisesignal components present in a monochrome type oftelevision signal. Since similar noise-signal components occur in eachof the color-signal channels but at phase relationships with respect toeach other, if each of the primary color images reproduced from thesignals in each of these color-signal channels had an equal electonV thehuman eye, the noise signals present would effectively cancel oneanother in each complete cycle of the subcarrier wave signal. rl'hus thenoise-signal componentspresent at 0, 120 and 240 would be addedvectorially land produce a net noise result of zero. However, it, iswell recognized that the sensitivity of the human eye to various colorshaving the same intensity is not identical. This may be determined in avery simple manner `by adjusting the gains in each of the channelsindividually related to the three color primaries in the reproducingdevice until the primary colors are such as to combine optically toproduce the sensation of white in the human eye. The brightness forwhite may be designated as unity and, if the brightness contributed byeach of the primary colors is measured, it will. be found that greencontributes-the most, red about haltA as much as green, and blue theleast` brightness sensation in the human eye; The fractional part ofunity contributed by each of the colors isthe relative luminosity of thecolor. The brightness sensations produced by the primary colors on thehuman eyey may be called the visual brightness effects of these colors.Because of this diterence in the visual brightness etfectsof thediierent primary colors, those added noise signals having similarelectrical energies and which cause the def velopment of spurious colorsdo not produce similar vis.- ual brightness effects and, therefore, donot cancel optically as otherwise might be. expected.

Though the previous paragraph describedthe effect of high-frequencyrandom-noise signal componentsY in 'a' system including a samplingdevice operating at a. sampling frequency, it shouldbe understoodv thatthe added noise-signal components thus produced may have' counterpartsin added components of signals other than randomnoise, such addedcomponents beingk producedI in a manY ner similar to the production ofthe added noise-signal components-just described. Thus interferencesignalshav-v ing a substantially constant frequency may occur at' the'upper end of the 4 megacyclepass band of the systerr in such a mannerthat they would not normally bel objectionable, since the eye is onlyslightly sensitiveto noise etlect's causing. high-frequency variationsin` the visual brightness of the image. but is much more' sensitivetonoise causing low-frequency brightness effects. Thus it thehigh-frequency interfering signals, by being hetero dyned with the.sampling frequency, become lowLfrequency interference signals, thereresult bothersome brightness variations. Similarly, high-frequencycomponents of the monochrome signalV mayY heterodyne with the sampling;

frequency to produeeobjectionable added lowsfrequency" components in thereproduced image. Therefore,.it isst'oi be understoodV that where Vtheterm added noisesignalf components is used hereinafter the expression isintended to include all added low-frequency interference of the typejust considered and of similar types.

It would be `desirable to be able Veiectively to eliminate the `visualbrightness fluctuations in the reproduced image caused -by the addedlow-frequency noise-signal cornponents separately aecting the dicrentcolorY signals. Since it is well known that noise which produces visualbrightness fluctuations of a low-frequency type is much more annoying tothe observer than noise which produces color fluctuations withoutresultant brightness fluctuations, the bothersome eiect of such visualbrightness uctuations may be eliminated effectively by converting thenoise-brightness fluctuations to noise-color luct'uations to which theeye is relatively insensitive. The copending application Serial No.159,212, previously mentioned, is directed to a system utilizing such amethod for diminishing these effects. The present invention is relatedto the one just mentioned, being directed to another type of system forovercoming the disadvantages just described.

Itis 'an object of the present invention, therefore, to provide a newand improved color-television system which avoids the aforementionedlimitations of the symmetricallyrdetected color system described.

It is another object of the present invention to provide a new andimproved color-television system of the type described having greatlyincreased compatibility for color and monochrome image reproduction.

Itis still another object of the invention to provide a new and improvedsignal-translating apparatus in a colortelevision receiver of a systemof the type described in which the amount of visual brightness noisepresent in a reproduced image is substantially no greater than thatpresent in a similar type of monochrome-television system.

- Itis afurther object of the invention to provide a new and-,improvedsignal-translating apparatus in a colortelevision receiver of a systemof the type described in v which'at least some of the visual 'brightnesnoise produced locally within the color-television receiver iseffectively canceled in the reproduced image.

AIt is a still further object of the invention to provide a new andimproved signal-translating apparatus in a color-television receiver inwhich a monochrome-signal component of a televisionrsignalsubstantially'determines the visualfbrightness of a reproduced image andthe colorsignal components determine substantially only the colorcharacteristics thereof, while anyl visual brightness elects producedthereby are substantially canceled.

VIn accordance with the present invention, there is provided asignal-translating apparatus for a color-television receiver whichutilizes a color image-reproducing device for reproducing an image froma predetermined group of primary colors.- This apparatus includes acircuit for supplying a composite television signal representative of acolor image and including a first portion having a band W1dth of greaterthan 0-2 megacycles representative of the visual lbrightness thereof anda second portion having a subcarrierwave signal having a speciiic bandwidth and modulated by at least a signal representative of thechromaticity of the image, the chromaticity signal undesirably tendingto aect the luminance in an image reproduced by the device. Theapparatus also includes a signal-deriving means coupled to the supplycircuit and including a network for translating said modulatedsubcarrier wave signal for deriving Afrom a specific phase thereof acontrol signal representative of the undesired luminance etfects of thelchromaticity signal and includes Va signalcombining device coupled tothe supply circuit-and the deriving means and responsive jointly to atleast the iirst portion and the control signal to develop a resultantsignal which is representative of at least the visual brightness of theimage and which includes a component inversely related to the undesiredluminance elects. Finally, the apparatus includesmeans for utilizing theresultant signal and the subcarrier wave signal in the image-reproducingdevice to reproduce the image, whereby the rst portion is effectiveprimarily to determine the visual brightness of the image and the secondportion is effective primarily to determine the chromaticity of theimage with any brightness changes due to the undesired luminance effectsbeing effectively eliminated.

In accordance with another embodiment of the present invention, yacolor-television system comprises a transf mitter which includes meansfor developing at least a first signal primarily representative of thevisual brightness of an image and substantially independent of itschromaticity. .The transmitter also includes means for developing asubcarrier wave signal modulated by at least a signal which is primarilyrepresentative of the chromaticity of said image said modulatedsubcarrier representative of the first signal and for translating asecond portion representative of the modulated subcarrier wave signal,the second portion tending to include undesired components aiiecting thevisual brightness in a reproduction of the image. The receiver alsoincludes signal-deriving means coupled to the signal-translating systemfor deriving from the second portion a control signal which is relatedto the component representative. of the relative luminosity and whichincludes a component representative of the luminance effects developedby the undesired components.V The receiver also includes asignal-combining device coupled to the signal-translating system and thesignal-deriving means for combining Vat least the first portion and thecontrol signal n to develop a resultant signal which is representativeof at least the brightness of the image and which includes componentsinversely related to the luminance eiects developed by the undesiredcomponents, and means for utilizing the resultant signal and thesubcarrier wave signal .to reproduce the image, whereby the resultantsignal determines the brightness of the reproduction of the image andsimultaneously substantially reduces anyk brightness changes which the.second portion tends to produce therein.

In accordance with a particular feature of the invention, thereisprovided in a color-television receiver apparatus for translating acomposite signal representative of an image in color and including afirst portion representative of the visual brightness of the image and asecond portion having a subcarrier wave signal modulated by at least asignal representative of the chromaticity of the image, the modulatedsubcarrier wave signal having a component representative Vof therelative luminosity-of elemental areas of the image. The apparatuscomprises a signal-translating system responsive to the composite signalfor translating at least the first portion and for translating avmodulated signal which'is representative of the modulated subcarrierwave signal and which includesundesired components tending to aliect thevisual brightness of the image. The apparatus includes a signal-derivingmeans coupled to the system'for deriving from the translated modulatedsignal a control signal which isvrelated to the `componentrepresentative of the relative luminosity and which includes a comvSiegel and the Saber-trier Wave signal to reproduce the image? wherebythe Resultaat Signal .iS representative f the brightness of the imagewith any brightness changes due to the undesired components beingeffectively eliminated.

In accordance with another feature of the invention, there is provided acolor-television transmitter comprising means for developing a pluralityof 9191 signals collectively representative of the brightness andchromaticity of an image and a first signal-translating channel coupledto the developing means and including a plurality of amplifier circuitsfor developing a first signal primarily representative of the visualbrightness of an image and substantially independent of itschromaticity. The transmitter also comprises a second signal-translatingchannel coupled to the developing means vand including a modulatorarrangement for developing a subcarrier wave signal and for modulatingthe subcarrier wave signal with the color signals to develop a secondsignal primarily representative of the chromaticity of the image andwhich includes a component representative of the relative luminosity ofelemental areas of the image. In addition, the transmitter comprises athird signal-translating channel coupled to the developing means andincluding a signalcombining circuit for combining the color signals todevelop a third signal representative of the brightness of the image anda modulator circuit for combining at least portions of the iirst, secondand third signals to develop a fourth signal representative of thechromaticity of the image modulated by a signal representative of therelative luminosity of elemental areas of the image. The transmitteralso comprises means for combining at least two of the first, second,third and fourth signals to form a composite signal.

The term monochrome signal as used herein refers to that portion of thecomposite video-frequency signal that would reproduce an irnage in astandard monochrome receiver and, therefore, is the signalrepresentative solely of the brightness of the image. Thus themonochrome signal can be considered substantially to be the average ofthe composite video signal over a complete sampling cycle; in otherwords, to be the composite video-frequency signal with any subcarriersignals and their modulation components removed, the latter componentshaving been inserted to translate the color characteristics of image.The monochrome signal may be a signal including equal amounts of allcolor signals or may be a signal comprised of dierent amounts of theprimary color signals.

The term color signal as used herein refers to a signal whoseinstantaneous value is proportional to the intensity of a primary colorof an elemental area of an image being scanned at the transmitter.Portions of the frequency band of this signal are designated ascolorsignal components.

The term composite coior-signal component as used herein refers to thatsignal formed by the modulation of a generated color wave signal orsubcarrier Wave signal by selected frequency components of the colorsignal or, in other words, by color-signal components. The compositecolor-signal component is a component of the composite video-frequencysignal and has amplitude and phase characteristics related to the colorcharacteristics of the image being televised, specifically, theamplitude thereof being related to the saturation of vthe color and thephase thereof being related to the hue of the color.

The term composite video-frequency component as used herein refers to asignal resulting from the combination of Athe monochrome signal and thecomposite colorsignal component.

The term brightness as used herein broadly refers to the brightnesseffects of a monochrome image or obiect. the degree of .lightness .ordarkness of the image or object, and speciticaliy relates to the opticalsensation.

produced by a signal composed .of signals yrepresenta tive of theprimary colors combined in any proportions other than proportionsrelated to ,the relative luminosities of' the colors.

The term visual brightness as used herein refers to the opticalsensation produced by a signal which is composed of amounts of thesignals representative of the primary colors proportioned in relationtov the relative luminesites of the colors,

For a better understanding of the present invention, together with otherand further objects thereof, reference is had to the followingdescription taken in connection with the accompanying drawings, and itsscope will be pointed out in the appended claims.

Referring to the drawings:

Fig. l is a generalized schematic diagram of a colortelevision systemand an associated chart including information relative to the signalstranslated through the system and which is utilized in explaining thepresent invention;

Fig. 2 is a schematic diagram of a color-television receiver embodyingthe present invention;

Fig. 2a is a circuit diagram of a unit in the receiver of Fig. 2;

Fig. 3 is an explanatory diagram utilized in explaining the operation ofthe receiver of Fig. 2;

Fig. 4 is a schematic diagram of a color-television transmitterembodying the present invention and Figs. 5 and 6 are schematic diagramsof modifications of the receiver of Fig. 2.

General description and expanotion of operation of the color-televisionsystem of Fig. 1

In describing the invention, a general description and explanation ofthe system as a whole including a brief consideration of the problemssolved by the invention and the manner of their solution will first bepresented. Referring now to Fig. 1, a color-television transmitter 10having an antenna system il, il and which may be of a type similar tothat previously described with reference to thev December 1949, issue ofthe RCA Review is arranged to televise a colored object 12. ln general,the radiated signal comprises a radio-frequency signal modulated by acomposite video-frequency signal having a band width of approximately 04 megacycies and including approximately a O-4 megacycle monochromesignal and a 3.6 megacycle color wave signal modulated at threedifferent phase points by color-signal components representative of thegreen, red and blue color characteristics of the image. The radiatedsignal is intercepted by the color-television receiver unit 13 by meansof antenna circuit 14, 14 thereof. The unit 13 may' be of anyconventional type suitable for intercepting a television signal and mayinclude the radio-frequency, oscillatormodulator, intermediate-frequencyand second detector Stages of a conventional ltelevision recever. Thecomposite video-frequency signal of the receiver signal is applied to asignal-translating apparatus 15 wherein the monochrome signal and thecolor-signal components are derived and applied to a colorimage-reproducing device 16. The device 16 may be of any conventionaltype suitable for reproducing color-television images While theapparatus 15 may, in prior systems, be the colorsignal detection portionof the receiver such as is described in the RCA Review articlepreviously referred to or, in the present system, be in accordance withthe teachings of the invention as described more fully hereinafter. ltis also possible that the ultimate derivation o f the brightness andcolor-signal components may occur in a portion of the device lr6.

Considering now in more detail the operation of thesystem of Fig. l andreferring particularly to the informa-V tion in the`associated charts,the televised object 12 may be considered to have a visual brightness Band 7 the charts. Thus, in prior systems, considering thecharacteristics of a single picture element or elemental area as thelelectronv beam impinges upon that area, the transmitter 10 analyzes`the color C of the area -in terms of the relative amounts of the threeprimary colors green, red and blue therein. This analysis develops colorsignals individually representative of theprimary colors.- At thetransmitter, the color signals are combined into a corn= posite signalkC and equal fractional amounts of the color .signals are also combinedadditively to develop a brightness signal l. The components of thesignal I are not combined in amounts proportionate to their relativeluminosity. The signals I and kC are translated through a common passband in the system in such a manner that the frequencies of the signalsrelating to color and brightness information at least partially overlap.Thus, because of the channel characteristics, noise, cross talk andother reasons previously considered, the signals designated I and kCtake the form in the receiver of the signals designated I and kC-I-kCu,wherein the signal kCu represents undesired color signals. Thebrightness signal I and each of the color signals related to the primarycolors green, red and blue are derived in the unit and applied v to theimage-reproducing device 16 to reproduce the color and brightness of thetelevised elemental area.

In the device 16, due to the relative luminosities or the dilerentcolors, as previously described, the color uctuations caused by theundesired color signal kCu cause undesired brightness fluctuations,designated as Bu, to appear in the reproduced elemental area as viewedby the eye. This conversion of undesired color effects kCu to undesiredbrightness eifects Bu occurs because, as the undesired color signalsvary in color, the eye sees these different colors at dierent brightnesslevels. As a result, a color C is reproduced which does not faithfullyrepresent the color C of the televised Vobject but which is acceptableto the eye. In addition, the visual brightness of the image is no longerB but becomes B-l-Bu, where Bu represents the undesired brightnesseffects resulting from the presence ofthe undesired color signal kCu.Thev visual brightness effect B-l-Bu can be represented in terms ofelectrical signals as L I(L+L.

where I represents a brightness signal as previously discussed, L isrepresentative of the relative luminosity of the elemental area of theimage being televised and Lu represents the luminosity eiect developedby the undesired color signalkCu. The present invention is directed tothe elimination of the factor Bu in each elemental area of thereproduced image.

Considering now the present system and referring to the information inthe lower portions of the charts, at the transmitter the visualbrightness B of the elemental area of the televised object is convertedto a signal IL which is proportioned in terms of the luminosity of theimage and, therefore, may Vbe described as a visual brightness signal.The visual brightness signal is one related to the relative sensitivityof the eye to the green, red and blue color phosphors in theimage-reproducing device. As in prior systems, the undesired colorsignal Cu is, at least in part, developed in the receiver 13 as a resultof the simultaneous transmission of the color and visual brightnesssignals through a common pass band in 'a frequency overlapping manner.To offset the brightness the luminosity effects in such area developedby the unv desired color signal Cu. In the apparatus 15,'the visualbrightness signal IL'is divided by the control signal L-l-Lnrand, as aresult, there is developed in that portion of the apparatus 15 directedto translating the signals representative of the Vbrightness of theimage a signal related to Lu which has brightness uctuations inverse tothose developed by the color signal Cu, as previously described.Consequently, the eye sees in the device 16 for each elemental area avisual brightness B and a color C. The undesired brightness uctuationsBu caused by the undesired color signal Cu are eliminated by thecorrection signal Lu. While the color signal C" may not be an ideallyfaithful reproduction of the color of the image, the quality thereof asviewed by the eye appears to be adequate and is much improved over thecolor of.' images reproduced in prior systems.

Thus, it is seen that the essential feature of the inven tion asembodied in a transmitter is the proportioning of the signalrepresentative of the visual brightness B inV It should be understoodthat the undesired color signal causing the undesired brightnessuctuations may include information desirable for purposes other thanbrightness, for example, may include acceptable color information whichin a predetermined type of color image-reproducing device may, inaddition to providing color, tend to disturb the luminance in a colorimage reproduced by such device Additionally, the term luminosityl orrelative luminosity, though employed herein as defining a certain typeof electrical signal Ihaving known characteristics when employed in apredetermined reproducing device, accurately only denes the light electof such signal in such device. That is, a signal as such is not aluminance signal but may be so classied when the light eect of suchsignal is considered with respect to a predetermined reproducing device.This light elect may vary when the signal is applied to different typesof such devices and dierent luminance corrections may be required forsuch variations.

General description of receiver of Fig. 2

Referring now to the receiver of Fig. 2, there is represented acolor-television receiver which includes a radiofrequency amplier 26 ofany desired number of stages having its input circuit connected to theantenna system 14, 14. Coupled in cascade to the output circuit of theampliiier 20, in the order named, are an oscillator-modulator 21, anintermediate-frequency amplifier 22 of one or more stages having outputterminals 3th, 36, a detector and automatic-gain-control (AGC) circuit23, a signaltranslating apparatus 15 to be described more fullyhereinafter, and a color image-reproducing device 16. The colorimage-reproducing device 16, including a cathoderay tube, is arranged todevelop from a composite videofrequency signal applied thereto from theunit 15 a color reproduction of the image'being televised. Devices ofthe type that may be used for such purpose are more fully described inan article entitled General description of receivers for thedot-sequential color television system which employ direct-viewtri-color kinescopes in the RCA Review for June i), at pages 228232.

There is also coupled to the detector 23 a synchronizing-signalseparator 24 having output circuits connected with conventionalhorizontal and vertical beam-deflecting windings inthe unit 16 throughline-scanning and eldscanning generators 25 and 26, respectively.Anoutput .circuit of the separator 24 is also connected to a colorwave-signal generator 27 through a terminal 28 in the Such a signal is avisualA unit 15. The output circuit of the AGC supply in the detector 23is connected to .the input circuitsof one'orv more of the tubes of theradio-frequency amplifier 20, the oscillator-modulator 21 and theintermediatefrequency amplifier 22 in a well-known manner.

A sound-signal reproducing unit 29 is also connected to y the outputcircuit of the intermediate-frequency amplifiery 22 and may include oneor more stages of intermediatefrequency amplification, a sound-signalvdetector, one or more stages of audio-frequency amplification and asound-reproducing device. Y

It will be understood that the units 20-27, inclusive, and 29 comprise apreferred circuit arrangement for the unit 13 of Fig. 1 and that, withthe exception of the unit 15, these units may have any conventionalconstruction and design, the details of which are well known in the arerendering a further description thereof unnecessary.

General operation of receiver of-Fig. 2

Considering briey the operation of the receiver of Fig. 2 as a whole andassuming for the moment that the unit 15 is a conventionalvideo-frequency signal-translating system, a desired modulatedtelevision wave signal including the visual brightness component IL anda color component C mentioned with reference to Fig. l is intercepted bythe antenna system 14, 14. The signal is selected and ampliied in theradio-frequency amplier and applied to the oscillator-modulator 21wherein it is converted into an intermediate-frequency signal. Thelatter signal is then selectively amplified in the unit 22 and suppliedto the detector 23 where its modulation components are derived. Thesemodulation components comprise a composite video-frequency signalrepresentative of an image in color and including a first portion ILrepresentative of the visual brightness of the image and a secondportion broadly designated vas C andrepresentative of the chromaticityof the image, the second portion including a component representative ofthe relative luminosity of elemental areas of the image. The tirst andsecond portions are translated through the unit 15 in a manner to bedescribed more fully hereinafter and applied to the control electrodesof the cathode-ray tube in the device 16 to modulate the intensity ofthe electron beam therein and to excite the image vscreen in the tube ofthe device 16 in a manner representative of the color of thetelevisedimage as more fully described in the RCA Review article for lune 1950,previously referred to herein.

The synchronizing-signal components of lthe received signal areseparated from the video-frequency components in the separator 24 andare used to synchronize the operation of the line-scanning andfield-scanning generators 25 and 26, respectively. These .generatorssupply signals of saw-tooth wave form which are 'properly synchronizedwith reference to the transmitted television signal and applied to apair of deecting windings for the cathode-ray tube in the device 16,thereby to deflect the cathode-ray beam therein in two directions normalto each other to reproduce on the image screen thereof a color image ofthe object being televised by the transmitter. There is also derived .inthe .separator 24 a synchronizing signal applied through the terminal 28Vtov the generator 27 for purposes lto be Vdescribed more fullyhereinafter.

The automatic-gain-control or AGC signal derived in the unit 23 isetective to control the amplification of one or more of the units 20, 21and 22110 maintain the signal input to the detector 23 and tothesound-signal reproducing unit 29 within a relatively narrow range for-a Wide range of received signal intensities.

The sound-signal modulated `wave signal accompanying the desiredtelevision wave Vsignal is also intercepted by the antenna system 14,14and, after'anrpliiication in the amplifier 20 and conversion,to-an'intermediate-frequency signal in the unit 21, it is translatedAthrough the ampliarrasar y lier 22 and applied ,to the-sound-.signalreproducing unit,

29,. ln the unit 29 it isamplilied andthe. sound-.signal modulation:components are derived therefrom, Ytheseximponents .being furtheramplified and kutilized by the re-v producing `device .in the unit 29 toreproduce4 sound -ina conventional manner.

Description of signal-translating `apparatus of F ig. 2

Referring now in particular to the signal-translating I apparatus 15embodying one form of the present invention, this apparatus comprises acircuit for supplying .the

aforementioned composite signal. More specifically, the` apparatusincludes a signal-translating system responsive to the composite signalfor translating a first portion thereof representative of the visualbrightness` of the `image and for translating a signal which isrepresentative of a second portion thereof, specifically, representativeof lthe chromaticity of the image, and which includes components tendingto affect the visual brightness of an image reproduced therefrom. Forexample, for translating the tirst portion, or visual brightness signal,the system comprises a lter network 33 having a pass band ofapproximately 0-4 megacycles and having an input circuit coupled throughan input terminal 31 to an output circuit of the detector 23 and anoutput circuit coupled to an inverse modulator 34. The system alsocomprises, in cascade, a lilter network ,35, an inverse modulator 36 and:a ilter network 37 coupled between the input terminal 31 and asynchronous detector 38. Each of the networks y35 and 37 is arranged tohaveV a pass band of approximately 2-4 megacycles. The system also mayinclude a lter network 39 having a pass band of approximately 0-2megacycles coupled between the terminal 31 and an input circuit of theinverse modulator 36, if the signal translated through the network 35includes brightness components as well as chromaticity components. Ifonly the latter components are translated through the network 35, thenthe units 36, 37 and 39 are not required and the output circuit of theunit 35 is directly connected to the detector 38. For purposes ofclarity and completeness, the more general of the two arrangements isdescribed herein. The channel including .units 35-37, nclusive, and 39translates a signal which is representative of the second portion of thecomposite signal, specilically that representative of the chromaticityof the Vimage but including components undesirably tending to aieet thebrightness of the image.

The signal-translating apparatus also comprises a signalderiving meanscoupled to the signal-translating system for deriving from the signalrepresentative of the second portion a control signal which is relatedto the component representative of the relative luminosity of elementalareas of the image and which includes a component Arepresentative of theundesired luminance effects developed by the translated components. Morespecifically, the signal-deriving means comprises, in cascade, the colorwave-signal generator 27, a phase-delay circuit 40, the synchronousdetector 38, a filter network 4l having a pass band of approximately 0-2megacycles, and an adder circuit 42, coupled between the terminal 28 andan input circuit of the modulator 34. The signal-deriving means alsoincludes a reference voltage source 43 coupled to an input circuit ofthe adder circuit 42 and which has an input circuit coupled to theterminal 31, The generator 27 may be of a conventional sine-wave typearranged to generate a signal in synchronism and phase with the colorsubcarrier Wave signal generated at the transmitter under the control ofa signal supplied thereto by the syn-l the Vunit .27 by an amountdetermined by the luminance angle of theqchromaticity signal, as will bedescribed more fully hereinafter. The rletcctorr may :be anyconventional type of `synchronous' pbase detector, examples of No.159,212 previously referred to wherein the phases of two'applied signalsare compared and a resultant signal derived from any differencetherebetween. The adder circuit 42 is a conventional means lforcombining two input signals in a manner which prevents feedback orundesired cross coupling of the signals in the input circuits. Thereference voltage source 43 may be a unidirectional potential source,for example a battery, Vwhich has a fixed voltage representative of therelative luminosity for white in the color system being utilized, asdescribed more fully hereinafter. Alternatively, the source 43 may be ameans for deriving such unidirectional potential from the compositesignal, for example from a predetermined amplitude portionr of avsynchronizing-signal pulse, if the system is `arranged to develop such apotential at the transmitter for derivation at the receiver.

The apparatus also. includes a signal-combining'device coupled to thesignal-translating system and to the signalderiving means for combiningat least the first portion and the control signal to develop a resultantsignal which is representative of' at least the brightness of the imageand which includes components inversely related to the undesiredluminosity effects developed by the translated components. Morespecifically, the apparatus includes the inverse modulator 34 coupled tothe network 33 of the signal-translating system and to the adder circuit42` of the signal-deriving means. A modulator of the type of unit 34 isdescribed more fully hereinafter with reference to Fig. 2a.

Description and explanation of operation of inverseY modulator of Fig.2a

Referring new to Fig.V 2a, there is represented a circuit arrangementthat may be utilized for either of the inverse modulators 34 or 36 4ofFig. 2. Considering this circuit with relation to the unit 34, theterminals 44 and 45 are arranged to be connected to the output circuitsof the units 33 and 42, respectively. The terminal 4S is coupled througha phase inverter 46 to a control electrode, specifically the outercontrol electrode, preferably of the remote cutoV type, of a pentodevacuum tube 48. The level of the signal applied to this outer controlelec trode is controlled by a Vresistor 49 connected Vbetween 'thelast-mentioned electrode and ground.` The input terminal 44 is coupledthrough a condenser 47 to an inner control electrode of the tube 48. v

In a mixer tube of the type'having ay remote cutoff outer signal grid,such as the tube 48 of Fig. 2a, the eg-ip curve of the remote'cutoi gridover a selected portion thereof, closely approximates a hyperbola, thatis, a curve in which one coordinate varies as the negative reciprocal ofthe other, thus representing a negative inverse function. Therefore, ifa signal is applied to the remote cutoff grid, there will be developedon the anode a negative inverse reproduction of the-applied signal.Since a conventional modulator normally producesV an output proportionalto the product of the applied signals, if a negative signal is appliedto the remote cutoff grid by the'phase inverter 46, the operation of thetube 4S is such that the resultant signal developed across the anodeload resistor represents the division of the signal applied to theterminal 44 by the signal applied -to the terminal 45. Thus thecomposite signal output of lter network 33 and, specifically, thatportion thereof representative of the visual brightness 'of the image,is divided by the signal applied from the added circuit `42.`

Erprmaton of operation of signal-translating apparatus ofFig. 2

In explaining the operation'of the apparatus 15 of Fig. 2, a generalexplanation thereof will rst be presented and then there will follow amore detailed explanation of portions thereof. Referring now to theoperationof the apparatus 15,;there is appliedto the terminal 31`andtranslated through the` filter network 33 to anrinput cir;

cuit of the inverse modulator 34 a composite. signal which may bedesignated as V(ILM-(IL) [Cel-Cul, this composite signal being morecomplex than the composite` will be used'to `enclose that portionA of asignal related Vto color.

Thus in the expression just presented (IL) is the visual brightnesssignal and the expressionIC-l-Cu] relates tothe chromaticity of theirnage.y In accordance v with the invention, `itis required that atleast the first portion of the composite signal, specifically ,theportion (IL) representative of the visual brightness of the image, betranslated through the network 33. The second portion of the compositesignal (IL) [C-i-Cul including both chromaticity signals andhigh-frequency brightness signals is translated through the filternetwork `35 and applied to yan input circuit of the inverse modulator36. The 0-2 megacycle low-frequency components of the visual brightnesssignal (IL) are, translatedl through the network 39 and appliedtoanother input circuit of the In the modulator 36, as will be.

inverse modulator 36. described more fully hereinafter, the signals (IL)[C-l-Cul translated through the unit 35 are divided by Vthesignals (IL)translated through the unit 39 to develop a signal [C-l-Cu] in theoutputcircuit of the modulator which is representative of the`chromaticity of the image and This chromaticity signal [C-l-Cul istranslated through the network 37 and applied to an input circuit of thedetector 38. As mentioned previously, if the signal translated throughthe network 35 contains' only the chromaticity information [C-i-Cu'LasAdescribed with reference to Fig. l, the units 36, `37and 39 may beomitted, the chromaticity signal [C-l-Cu] being'applied directly tothedetector 38. The development of signals of this andv of other typeswill be described more fully hereinafter with reference tothe'transmitter of Fig. 4.

The signal developed by 'the generator 27 is delayed in phase inthe'unit 40 by a certain'amount, as described hereinafter, and -is-applied to another input circuit of the detector 38. They detector 38effectively samples the signal [C4-Cu] applied thereto from the network37 at a phase angle related to the phase delay of the sampling signalapplied to theunit 38 from the generator 27 to Y derivev a controlsignalL [L-l-Lcul. The latter signal` is related to that component ofthe chromaticity signal which is representative `of the relativeluminosity Lc of ,theelemen'tal vareas of the image and which alsoincludesv a component Leu representative of the undesired luminos ityeifects developed by ,the undesired color signal [Cu] in thechromaticityfsignal'." 'The low-frequency corn-v ponents ofthis controlsignal [Le-l-Leu] representative of that portion. of the luminositycomponent related to chromaticity are translated ythrough the` network41 and combined in the adder4 circuit 4 2 'with a signal Lw developed inthe unit 43 and which represents the luminosity of white in the systembeing. employed. The resultant signal L-{L/u, Vrepresenting therelative'luminosity of Hele-- mental areas of the image plus therelative luminosity or visual brightness effectsu ofathel undesiredcomponents in thefcolork channel, is 'then applied as a control signalto the input circuit of the inverse modulator 34. In'the K unit 34e-thecomposite signal, or at least the first portion thereof, isj divided`bythe control signal applied from the-adder'cii'cuit 42 atordevelop aresultant signal which is translated through the.t'erminal 32 andappliedto thel input circuit of the image-reproducing.device 16. Thedivision may be expressedmathematically as follows:

present, it is seen that:

IL ILC-PILCH, w (Drawi 'reduceb to @H1022 If there are undesired colorcomponents Cu present, resulting in the development of a factor Luelfectively occurring in the numerators of thetwo parts ofthe aboveexpression, then the `factor Lu in the denominators thereof effectivelycancels therewith. It is to be understood that Lu eiectively occurs inthe numerators due to the electrical and optical effects of thecomponent Cu.

To understand the invention, it is helpful to examine in more detail themanner in which the primary Vcolors green, red and blue are utilized totranslate and reproduce the chromaticity of a televised image. Referringnow to Fig. 3, there is represented a color diagram in triangular formhaving the color primaries at the points of the triangle. This trianglerepresents that area of the color spectrum which the primaries green,designated by G, red, designated by R, .and blue, designated by B, eachcomprising a specic band of wave lengths, are capable of reproducing.vMore details with respect to such a triangle may be found in athree-part article entitled Color fundamentals for TV engineers byDonald G. Fink, Electronics, December E50-February 195i, and,specifically, on page 83 of the January 1951 issue. The circle enclosingthe .triangle GRB represents the cyclic phases in which the colors G, Rand B modulate the subcarrier wave signal, vgreen being assumed tomodulate at zero phase, red Vat 120 and blue at 240 of a cycle of thesubcarrier wave signal. As ypreviously described, the colors G, R and Beach haverelative luminosity, determined by the relative brightnesscontributions of equal energy amounts of each color .combined to formwhite. For one particular set of such primaries, green has a relativeluminosity of 0.59, red a relative luminosity of 0.34, and blue 0.07 anda white signal W, represented at the center of the triangle will bereproduced by the combination of equal amounts of these colors. Thewhite signal W also has a relative luminosity depending upon therelative luminosities of the green, red and blue signals and this factoris fixed for a given set of primaries.

It is seen that luminosity, in general, is a factor related to thebrightness sensations produced in the eye by the different colors. Thus,if a line A is drawn from the point of the triangle R to a point on theVside of the triangle BG having the same relative luminosity, that is,0.34, all colors represented by the line A will have vequal relativeluminosities and, therefore, any change from one color to another alongthe line will produce no change in visual brightness, since there is nochange in the relative luminosity. if there is erected a line V normalto that line, for example, through the point W, such a line thenrepresents the maximum variation in luminosity for all colors defined bythe triangle GRB. lf the line V is drawn to intersect the circlerepresenting the sampling cycle, it is seen that there is a phase angleof the modulated subcarrier wave signal which represents the variationin brightness for the color represented by each cycle of the subcarrierwave signal, that is, the color for each elemental area of the image.Since the present invention is directed to having color signals producethe least visible brightness disturbance in the reproduced image, it isits proposed in accordance with the present invention that in each cycleof the subcarrier wave signal there bederived at the angle 6 'of theline V a control signal which represents the relative luminosity of thecolor being transmitted during that cycle .and also the luminanceeffects of any color components that have been developed whichundesirably .affect the brightness of an image reproduced therefrom.

In viewrof the above, in order to derive the luminosity control signal[Lc-l-Lcul at the angle 0, the phase-delay circuit itl is proportionedto cause the detector 3S to sample the chromaticity signal appliedthereto from the unit 37 at the angle 0. The control signal [LH-Leu] isproportional to the relative luminosity for each elemental area of theimage and inherently includes not only the relative luminosity effectsLc caused by the televised color of the image but also includes theundesired relative luminosity effects Leu caused by the color signal.Since this control signal is only representative of the relativeluminosity [Lc-I-Lcu] of the area contributed by the color, the signal[Lc-i-Lcu] .is combined with the luminosity signal Lw for white in theunit 42 to develop the complete control signal L+Lu. The latter controlsignal, as has been described, combines with vthe brightness signal inthe inverse modulator 34 to develop the desired brightness result in.the image reproduced by the device 16.

By means .of the arrangement described, any undesired visual effectsproduced by the color-signal components in the reproducing device may beeffectively canceled by such employment of the luminosity component Lurepresentative of the undesired visual brightness of the colorcomponents inversely in the brightness channel of the system by .meansyof the inverse modulator 34.

Description of color-television transmitter of Fig. 4

In .order that a receiver in accordance with the present invention beoperative, -it is necessary that complementary operations occur at thetransmitter and thereceiver of the color-television system. Thearrangement at a receiver of the system, .to develop a control signalwhich is effective in diminishing the undesired visual brightness eectsproduced by the color components developed in the system, has beendescribed above. An operation complementary to the inverse modulation atthe receiver is required at the transmitter in order that the signals inthe output of the inverse modulator in the receiver circuit willfaithfully represent the brightness and the chromaticity of thetelevised image. The composite video-frequency signal conventiallydeveloped in a color-television receiver is here modulated in terms ofthe relative luminosity of the signals which compose the compositevideo-frequency signal. The transmitter represented by Fig. 4 providesan arrangement .to -effect such modulation.

Referring now to Fig. 4, the transmitter represented therein comprises asignal-developing apparatus 50 which is arranged to develop colorsignals related to corresponding colors of an image being televised andincluding brightness information with relation thereto. The apparatus5!) may include television cameras and related equipment conventionallyused to develop color signals of the type described. Theequipment in theapparatus 50 utilized for timing the operation of the cameras is alsocoupled to a color wave-signal generator 51 and to an output amplifier52. individual output circuits of the apparatus 5t), supplying the'0-4megacycle red, green and blue color signals, are coupled to individualones of kfilter networks 53a, 53h and 53C, each having a pass band ofapproximately 0-2 megacycles, .and to individual-ones of amplifiers 54a,54b and 54e. These individual output circuits are also collectively.coupled to an .adder circuit 55. Individual ones of the networks'Sila-53e, inclusive, are coupled to synchronous modulators 56a, Sb and`56C, respectively, the outputcircuits vof which are individualiycoupled to input circuits of an adder 15 s circuit 57. Coupled incascade to the output circuit of the unit 57, and in the order named,are an inverse modulator`58, a modulator 59, a lter network 60 having apass band of approximately 2-4 megacycles, an adder circuit 61, theamplifier 52 and a signal-transmission apparatus 62 having the antennaVsystem 11, 11. The inverse modulator 58 may be of the type illustratedin Fig. 2 and described above. The apparatus 62 may be of a conventionaltype including a wave-signal modulation circuit, power amplifier, andthe antenna means 11, 11 for radiating the modulated wave signal` Theoutput of the generator 51 is coupled directly to the modulator 56a andthrough delay lines 63b and 63e to the modulators 56b and 56e,respectively. The delay lines 6311 and 63C are vproportioned to delay,the signal generated in the unit 51 by 120 and 240, respectively, toAeffect modulation of the signal generated in the unit 51 at differentphase points thereon as previously mentioned. The adder circuit 55 isconnected, through a iilte'rl network 64 having a pass band ofapproximately -2 megacycles, to an input circuit of the inversemodulator 58. Individual output circuits of the amplifiers54a-54c,inclusive, are coupled to individual input circuits of an addercircuit 65, the output circuit of which is coupled through afilternetwork 66 having a pass band of approximately 0-4 megacycles, toan input circuit of the adder circuit 61 and through a filter network 67having a pass band of approximately 0-2 megacycles to an input circuitof the modulator 59.

The amplifiers 54a-54c, inclusive, are so proportioned that each has again representative of the relative luminosity of the color representedby the signal being translated therethrough. Thus, if the amplifiers54a-54c, inclusive, are arranged individually to translate signalsrepresentative of the green, red and blue characteristics of the image,respectively, the gains of these ampliers would be adjusted in the ratioof 0.59, 0.34 and 0.07 if the primary colors discussed with reference toFig, 3 are utilized. Ihe synchronous modulators 56a-56c, inclusive, maybe of a type described in the copending application Serial No. 159,212previously mentioned herein. Specically, they are arranged to eiectmodulation of the subcarrier wave signal developed in the unit 51 by theindividual color signals translated through the units 53a-53c,inclusive, at phase points on the subcarrier wave signal of 0, 120 and240, respectively. The adder circuits 55, 57, 61 and 65 may be of anyconventional type for combining the signals applied to the inputcircuits thereof in an additive manner.

Explanation of operation of color-television transmitter of Fig. 4

Considering now the operation of the transmitter of Pig. 4, color wavesignals related to the basic color characteristics of the televisedimage, specifically related to the colors green, red and blue thereof,are developed in the apparatus 50 in any conventional manner. Thesesignals are then individually applied to the networks 5311-530,inclusive, translated therethrough and individually applied to themodulators 56a-56c, inclusive. In the modulators 56a-56c, inclusive, thesignals modulate the subcarrier wave signal applied thereto by thegenerator l at different phase positions thereon, specifically at 0phase in the modulator 56a, at 120 in the modulator 5611 and at 240 inthe modulator 56e. The 120 and 240 phase delays of the signal generatedin the unit 51 are effected by the delay lines 63b and 63e,respectively. The output signals of the modulators 56a-56c, inclusive,are combined additively in the circuit 57 and applied to an inputcircuit of the inverse modulator 58. Y

The color signals developed in the output circuits of the apparatus arealso individually applied to the ampliiers ,5de-54e, inclusive,whereinthe amplitudes of the signals related to thek green, red and bluecharacteristics of the image are controlled in proportion to therelative luminos- 54a-54c,' inclusive, are combined additively in thecircuit 65 to form the visual brightness signal represented by the term(IL) considered with reference to Fig. l. The signal (lL) is translatedthrough the network 66 and applied to an input circuit of the addercircuit 61. A 0-2 megacycle portion of this signal is also translatedthrough the network 67 and applied to an input circuit of the modulator59. i

The individual color signals in the output circuit of the apparatus 50are also applied to the adder circuit 55 wherein they are combinedadditively to develop a signal (I) representative of theV brightness ofthe image. The signal (I) is composed of equal amounts of the green, redand blue color signals regardless of their relative luminosity, that is,the sensitivity of the eye to the brightness of these signals, and the0-2 megacycle component thereof is translated through the network 64 andapplied to an input circuit of the inverse modulator 58. The signalapplied to the modulator 58 from the adder circuit 57 represents thechromaticity [C] of the image but also includes a 0-2 megacyclebrightness component (l) and, thus, may be designated by the term [IC].In the in verse modulator 58 the component (I) is canceled therefrom asa result of the division thereof by the signal (I) translated throughthe network 64 and, as a result, a signal [C] representative solely ofthe chromaticity of the image is developed in the output circuit of themodulator 5S and applied to the input circuit of the modulator 59. Inthe modulator 59 the chromaticity signal [C] is modulated by the visualbrightness signal (IL) translated through the network 67 and there isdeveloped in the output circuit thereof a signal designated (IL) [C] andrepresentative of the product of the chromaticity signal and the visualbrightness signal. The 2-4 megacycle portions of this signal, includingthe color subcarrier and at least a portion of the side bands thereof,are translated through the network 60 and combined in the adder circuit61 with the visual brightness signal (IL) translated through the network66 to form the composite video-frequency signal (1L){ (IL) [C]previously considered with respect to the receiver of Fig. 2. Thisvcomposite video-frequency signal is Vfurther amplified in the amplifier52 and combined therein with the synchronizing signals developed in theunit 50 to form a signal including both Video-frequency andsynchronizing information. The latter signal is utilized to modulate acarrier-wave signal in the apparatus 62 and is radiated as a televisionsignal by the antenna system 11, 11.

It is thus seen that the transmitter of Fig. 4 is arranged to develop acomposite video-frequency signal in which the color and brightnesscomponents thereof are propor-Y tioned in terms of the relativeluminosity of the colors which combine to compose this signal. In thismanner, an inverse operation can occur at the receiver, as previouslydescribed with reference to Fig. 2, without affecting the fidelity ofthe color and brightness signals. By such inverse operation at thereceiver, the undesired brightness effects previously discussed aregreatly diminished and the colortelevision system is more effective inpresenting an acceptable reproduction of the televised image.

In considering the transmitter of Fig. 4, the manner in which acomopsite video-frequency signal, proportioned in terms of the relativeluminosity of its components, is developed, has been described andexplained. It should be understood that composite video-frequencysignals other than the one described may be .developed and utilized,depending on the system and mode of signal translation selected. Thus,only the monochrome component may be proportioned in terms of therelative luminosity of the components to form the signal (IL) and thechromaticity component [C] combined therewith in the unit 61 to developa composite video-frequency signal (IL)'-i-[C]. In such case, the lilternetwork 67 and the modulator 59 are omitted at the transmitter, and thereceiver is correspondingly simplified as described with reference toFig. 2. Similarly, if desired, the chromaticity signal may be [IC] andthe adder circuit 55, the filter network 64, the inverse modulator S,the modulator 59 and the filter network 67 may be omitted but thisrequires a more complex arrangement at the receiver to eliminate thebrightness component (I) from the color signal in order to derive the[Lvl-Leu] signal. The manner in which such brightness component may beeliminated by including units at the receiver to derive the component(l) from the brightness signal and an inverse modulator to eliminate thebrightness component (I) from the color is understand.- able fromsimilar operations described herein. Other possibilities are equallyevident, being limited only by the need to proportion the brightnesssignal at the transmitter in terms of L and to derive from the colorsignal at the receiver either directly or indirectly a signalrepresentative of L-l-Lu.

Description of signal-translating apparatus of Fig. 5

With respect to the receiver of Fig. 2, there has been described asignaLtranslating apparatus by means of which a signal, proportional tothe relative luminosity of elemental areas of the reproduced image andincluding a control signal related to the visual brightness effectsdeveloped by components of the chromaticity signal, can be derived. Thederived relative luminosity signal is then employed in combination withthe visual brightness signal to eiect a reduction in the undesiredvisual brightness effects caused by color-signal components. To obtainthe derived relative luminosity signal L-l-Lu in the apparatus theredescribed, a luminance factor [Ln-l-Lcu] related solely to thechromaticity of the image was first derived and added to a fixedluminosity factor Lw related to white for the color primaries beingemployed in the system to obtain the control signal L-l-Lu. Theapparatus of Fig. 5 presents an arrangement wherein the signal L-l-Lumay be directly derived from the composite video-frequency signal thussimplifying the signal-translating apparatus. Since the apparatus ofFig. 5 is related to the apparatus of Fig. 2, similar units in bothembodiments are designated by the same reference numerals and analogousunits by the same reference numerals with a factor of 500 added thereto.

In the apparatus of Fig. 5, the filter network 33 is coupled between theinput terminal 31 and an input circuit of an amplifier or modulator 70.The output circuit of the filter network 39 is coupled through a pair ofseriesconnected resistors 71 and 72 to ground. The junction point of theresistors 71 and 72 is directly connected to another input circuit ofthe amplier 70 and through a resistor 73 to an output circuit of anamplifier 74. The resistors 71-73, inclusive, form a signal-combiningcircuit. There is provided a filter network 75 having a nonlinearfrequency-response characteristic over a pass band of approximately 0-4megacycles, the response being substantially uniform in the region of0-2 megacycles and sub"- stantially uniform in the region of 2-4megacycles but of different values in these two regions as will beconsidered more fully hereinafter. The network 75 is coupled between theinput terminal 31 and an input circuit of the sampling device 538. Thesampling device 538 is similar in structure to the synchronous detectorin the apparatus 15 of Fig. 2 except that it operates more in the natureof an electronic switch to select a portion of the 0-4 megacycle signaltranslated through the network 75 at a time determined by the signalfrom the generator 27. The output circuit of thenetwork 41 is connectedto an input circuit of the amplifier 74, another input circuit of whichis connected to the junction of resistors 71 and 72 and to an inputcircuit of the amplifier 70. The output circuit of the amplifier 70 isconnected to the terminal- 32.

The pass band of the network 75 is proportioned to translate the 0-2megacycle portion of the 'signal applied thereto so that the response ofthe network with respect to 'it this portion is representative of Lw andthe response with respect to the 2-4 megacycle portion is representativeof Le, where both Lw and Lc have the same scale factor. The scalefactors of the monochrome and subcarrier signals are normally different,due to an arbitrary relationship between the maximum amplitude of thecolor subcarrier wave signal and the brightness signal utilized in thesystem and developed at the transmitter when the color and brightnesssignals are combined. The relative responses of the two portions of the0-4 megacycle signal may differ by factor x and the composite signal canbe expressed as:

Since the amplitude of the signal (IL) is to be representative of Lw andthe signal x(lL) [CL when sampled at the luminance angle 6, is to havean amplitude representative of Le, both Lw and Lc having the same scalefactor, it is seen that:

and that if the response of the portion of the channel through which the0-2 megacycle portion is translated is assumed to be related to Lw, theresponse of the portion through which the signal component including Lcis translated should be and the ratio of the responses in the twoportions is 1 xLw More specifically, for a system of the type beingdescribed with one specific set of receiver color primaries, theresponse of the channel through which the signal representative of Le istranslated should be approximately 'Ms of the response of the 0-2megacycle channel. Assuming thatx=l at the transmitter and all channelsother than the network 75 through which the two portions of the signalare translated have uniform response for all 0-4 megacycle signals, thepass band of the network 75 is proportioned to have unity response forthe 0-2 megacycle portion and 0.875 response for the 2-4 megacycleportion.

Each of the amplifiers and 74 is a conventional variable-gain typeeffectively operating as a modulator, the gain thereof being controlledby an applied signal effectively to multiply the applied signal byanother applied signal. Because of this function, these amplifiers maybe designated as modulators. Any conventional amplifier of this type,being well known in the art, may be employed.

Explanation of operation of signal-translating apparatus of Fig. 5

Considering now the operation of the apparatus of Fig. 5,v the compositevideo-frequency signal is applied lto the terminal 31, translatedthrough the network' 33 and applied to the input circuit of the amplier70`. As described with reference to the apparatus of Fig. 2, this signalincludes at least a first portion representative of vthe brightness ofthe image. Specifically, it includes such portion and a second portion,the latter portion being representative of the color or chromaticity ofthe image. A low-frequency portion representative ofthe 'brightness ofthe image and designated (IL) is translated through the network 39 andis developed across the resistors 71 and 72. The compositevideo-frequency signal, having the 0-2 megacycle and the 2-4 megacycleportions thereof differently translated in the manner previouslydescribed, is translated through the filter network 75 and applied tothe sampling device 538 wherein, by means of the signal applied from thegenerator 27 as previously described, a signal representative of the'luminosity of each of the elemental areas of the image The amplifier 74during the initial instant vof operation develops in the output circuitthereof, in a conventional manner, the signal -(IL)(L-|-LU)(A), where Arepresents the gain of the amplifier 74. The latter signal is translatedthrough the resistor 73 and develops a potential across the resistor 72.The signal (IL) translated through the network 39 and the signal (IL)(L4-Lu) (A) translated through the amplifier 74 combine to develop aresultant signal which controls the gain A of the amplifiers 70 and 74.This resultant signal is of such a nature that it tends to make thesignals (IL) and (IL) (L+Lu)(A) equal. As a result, the ampliers 70 and74 are controlled so that each has a gain:

(A)L+L..

Thus, as the composite video-frequency signal is translated through theamplifier 70, it effectively is divided by the signal L-l-Lu and becomesan output signal similar -to that described with reference to theapparatus 15 ofv Fig. 2. This signal may then be used in animagereproducing device in the manner previously Ydescribed withreference to the apparatus of Fig. 2.

Description of apparatus f Fig. 6

The apparatus of Fig. 6 represents another and somewhat simplerarrangement for accomplishing-theobjects of the invention, some featuresof which are more fully described in applicants copending applicationentitled Color-Television Signal-Translating System, Serial No. 262,309,filed December 18, 1951. Since the apparatus represented by Figs. 2, and6 of the present application are related, similar units in each thereofare designated bythe same reference numerals and analogous units of Fig.6 by the same reference numerals as used with respect to Fig. 2 with afactor of 600 added thereto.

The terminals 30, 30, being a pair of input terminals to the apparatusof Fig.Y 6, are arranged to becoupled vto a pair of terminals such asthe terminals 30, k30 in the output circuit of theintermediate-frequency amplifier. 22 of Fig. 2. Coupled in cascade withthe ter .minals 30, 30 are an intermediate-frequency amplifier 80, anadder circuit 81, an amplifier 670, a band-pass filter network 82 havinga pass band determined by the intermediate-frequency color subcarrierand its side bands, `for example of 22-24 megacycles, and an amplifier83. There are also coupled in cascade with the terminals 30, $10 asynchronizing-signal detector 84, a color wavesignal generator 627, aphase-delay circuit 640, a sampling device 638 and the filter network41, the output of the network 41 being coupled to an input circuit ofthe adder circuit 81. The synchronizing-signal detector 84 is arrangedto derive a synchronizing control signal for the 4generator 627. Thegenerator 627 has elements so proportioned as to develop a wave signalhaving a frequency related to the intermediate frequency of theamplifier, for example a frequency of 22.5 megacycles, and, in someapplications as described in the inventors copending applicationreferred to above, the intermediate-frequency signal itself, having afrequency, for

example', of 26 megacycles, may be employed instead of utilizing a localgenerator such as the unit 627. For this reason, the units 34 and 627are shown as being .connected to the terminal 30 and to the unit 638,respecthat the intermediate-frequency color subcarrier signal', and itsside bands are not translated therethrough while the signal -(IL)(L-t-Lu) (A) is translated therethrough is coupled between the outputcircuit of the amplifier 670 and the resistors 73 and 72. The outputcircuit of the band-pass filter network 82 is coupled to ground througha pair of series-connected resistors 86 and 87 while an amplitudedetector 89 is coupled from the output circuit of amplifier 670 to thejunction of the resistors 86 and 87.

The apparatus of Fig. 6 isarranged to utilize a signal of the typedeveloped in the network 75 of Fig. 5, which signal may be locallydeveloped by means of a filter network having a nonuniformfrequency-response characteristic, such as the unit 75 of Fig. 5, or itmay be developed at the transmitter in the system. With respect to theapparatus of Fig. 6, it is assumed that such a signal has been developedat the transmitter and is applied to the terminals 30, 30 as amodulation signal of a subcarrier wave signal having a frequency in theintermediate-frequency band of the receiver.

Explanation of operation of apparatus of Fig. 6

Considering now the operation of the apparatus of Fig. 6, theintermediate-frequency signal modulated by the 0-4 Vmegacycle compositevideo-frequency signal is applied to the sampling device 638 wherein, atthe proper phase ineach cycle ofthe intermediate-frequency subf carrier,a control signal, related to the luminosity of an elemental area of thereproduced image and having the form (IL) (L-l-Lu), is derived. Thissignal is translated through the network 41 and combined in the addercircuit 81 with the modulated intermediate-frequency signal translatedthrough the amplifier 80. It will be seen that the signals translatedthrough the unit and the unit 41 will occupy different portions of thefrequency spectrum. These two bands of signals are then translatedsimultaneously through the amplifier 670, and the low-frequency portion,specifically the 0-2 megacycle portion of the signal translatedtherethrough, is translated through the network 85 and appears in theoutput circuit thereof in the form of the signal '-(IL) (L-l-Lu) (A).This signal combines with the signal'translated through the network 39to control the gain (A) of the amplifier 670 in the manner previouslydescribed with reference to` the apparatus of Fig. 5. Thus, the signaltranslated through the band-pass filter network 82 and the amplitudeVdetector 89V is a corrected signal of the type previously described,modified by a control signal related to the lumi-- nosity inverselycombined therewith. The band-pass filter network 82 translates only theintermediate-frequency color subcarrier wave signal and its side bands,specifically a signal having a band width of 22-24 megacycles. Theamplitude detector 89` derives a signal related to the brightness of theimage modified bythe control signal developed by the controlled gain ofthe amplifier 670. The signals translated throughl the network 82 andthe detector 89 are simultaneously developed across the re'- sistors 86,87 and translated through the amplier 83'. They are then applied throughthe terminal 32 to the image-reproducing device in the manner describedmore fully in applicants last-mentioned copending application.

vThe combined signals are similar to the previously deplished at thereceiver by deriving from thev chromaticity 1zignalfoi from thelchrm'naticity signal and the brightness signal, a signal which isrelated to the relative luminosity of elemental areas of the reproducedimage. This latter signal includes a component related to the undesiredrelative luminosity of the color components and is combined with thebrightness component of the composite video-frequency signal in such amanner that it will offset in the reproduced image the brightness electscaused by such color components when the image is viewed by the eye. Itshould be understood that the composition of the compositevideo-frequency signal is in general not pertinent to the invention andany number of diierent compositions may be employed, provided that thebrightness component of the composite Video-frequency signal isproportioned in terms of relative luminosity at the transmitter and aluminosity-type signal is derived at the receiver and combined inverselywith the proportioned brightness component.

While there have been described what 'are at present considered to bethe preferred embodiments of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,aimed to cover all such changes and modiiications as fall within thetrue spirit and scope of the invention.

What is claimed is:

l. Signal-translating apparatus for a color-television receiver whichutilizes a color image-reproducing device for reproducing an image froma predetermined group of primary colors comprising: a circuit forsupplying a composite television signal representative of a color imageland including a first portion having a band width of` greater thanl 2megacycles representative of the visual brightness thereof and a secondportion having a subcarrier wave signal having a specific band width andmodulated by at least a signal representative of the chromaticity of theimage, said chromaticity signal undesirably tending to affect theluminance in an image reproduced by the device; signal-deriving meanscoupled to the supply circuit and including a network for translatingsaid modulated subcarrier wave signal for deriving from a specific phasethereof a control signal representative of the undesired luminanceeffects of said chromaticity signal; a signal-combining device coupledto said supply circuit and said deriving means and responsive jointly toat least said iirst portion and said control signal to develop aresultant signal which is representative of at least the visualbrightness of said image and which includes a component inverselyrelated to said undesired luminance effects; and means for utilizingsaid resultant signal and said subcarrier Wave signal in theimage-reproducing device to reproduce said image, whereby said irstportion is eiective primarily to determine the visual brightness of saidimage and said second portion is effective primarily to determine thechromaticity of said image with any brightness changes due to saidundesired luminance eects being effectively eliminated.

2. Signal-translating apparatus for a color-television receiver whichutilizes a color image-reproducing device for reproducing an image froma predetermined group of primary colors comprising: a circuit forsupplying a composite television signal representative of a color imageand including a iirst signal having a band width of greater than 0-2megacycles representative of the visual brightness thereof and a secondsubcarrier wave signal having a band width of more than l megacycle andmodulated at a predetermined phase by at least a signal representativeof the chromaticity of the image, said chromaticity signal underisablytending to affect the luminance in an image reproduced by the device;signal- 'deriving means coupled to the supply circuit and including anetwork having a pass band substantially equal to said band width ofsaid subcarrier wave signal for .translating said modulated subcarrierwave signal for deriving from said predetermined phase thereof a` cotrolsignal representative of the undesired luminance effects of saidchromaticity signal; a signal-combining device coupled to said supplycircuit and said deriving means and responsive jointly to at least saidiirst signal and said control signal to develop a resultant signal whichis representative of at least the visual brightness of said image andwhich includes a component inversely related to said undesired luminanceeiects; and means for applying said resultant signal and said subcarrierwave signal to the image-reproducing device to reproduce said image,whereby said first signal is elective primarily to determine the visualbrightness of said image and said second signal is effective primarilyto determine the chromaticity of said image with any brightness changesdue to said undesired luminance effects being electively eliminated.

3. Signal-translating apparatus fora color-television receiver whichutilizes a color image-reproducing device for reproducing an image froma predetermined group of primary colors comprising: a circuit forsupplying a composite television signal representative of a color imageand including a rst signal having a band width of approximately 0 4megacycles representative of the visual brightness thereof and a secondsubcarrier wave signal having a band width of approximately 24megacycles and modulated at a predetermined phase by at least a signalrepresentative of the chromaticity of the image, said chromaticitysignal undesirably tending to aiect the luminance in an image reproducedby the device; signal-deriving means coupled to the supply circuit andincluding a band-pass lter network for translating said modulatedsubcarrier wave signal and for deriving therefrom at said predeterminedphase thereof a control signal representative of the undesired luminanceeiects of said chromaticity signal; a signal-combining device coupled tosaid supply circuit and said deriving means and responsive jointly to atleast said first signal and said control signal to develop a resultantsignal which is representative of at least the visual brightness of saidimage and which includes a component inversely related to said undesiredluminance effects; and means for applying said resultant signal and saidsubcarrier wave signal to the image-reproducing device to repro'- ducesaid image, whereby said iirst signal is effective primarily todetermine the visual brightness of said image and said second signal iseffective primarily to determine the chromaticity of said image with anybrightness changes due to said undesired luminance effects beingeffectively eliminated.

4. Signahtranslating apparatus for a color-television receiver whichutilizes a color image-reproducing device for reproducing an image froma predetermined group of primary colors comprising: a circuit forsupplying a composite television signal representative of a color imageand including a iirst portion representative of the visual brightnessthereof and a second portion having a subcarrier wave signal modulatedby at least a signal representative of the chromaticity of the image,said Wave signal as supplied having a component representative of atleast a fraction of the luminance in an image reproduced by the deviceand undesirably tending to atectthe luminance in the image;signal-deriving means coupled to the supply circuit for deriving fromsaid modulated subcarrier wave signal a control signal including saidcomponent and representative of the undesired luminance effects; asignal-combining device coupled to said supply circuit and said derivingmeans and responsive jointly to at least said first portion and saidcontrol signal to develop a resultant signal which is representative ofat least the visual brightness of said image and which includes acomponent Vinversely related to said undesired luminance elects; andmeans for applying said resultant signal'and `said subcarrier wavesignal to the image-reproducing device to reproduce said image, wherebysaid resultant signal is representative of the visual brightness of saidimage and any brightness changes due to said undesiredv luminance eec'tsare effectively eliminated.

5. Arcelor-television system comprising: a transmitter including meansfor developing at least a first signal primarily representative of thevisual brightness of an 'image and substantially independent of itschromaticity, means for developing a subcarrier Wave signal modulated byat least a signal which is primarily representativey of the chromaticityof said image said modulated subcarrier wave'signal including acomponent representative of the relative luminosity of elemental areasof the image, means for combining said developed signals to form acomposite signal, and means for transmitting said composite signal; anda receiver for said transmitted'signals including a signal-translatingsystem for translating a first portionV of said composite signalrepresentative of said first signal and for translating a second portionrepresentative of said modulated subcarrier wave signal, said secondportion tending to include undesired components affecting the visualbrightness in a reproduction of said image, including signal-derivingmeans coupled to said signal-translating system 'for deriving from saidsecond portion a control signal which is related to said componentrepresentative of said relative luminosity and which includes acomponent representative of the luminance effects developed by saidundesired components, including f a signal-combining device coupled tosaid signal-translating system and said signal-deriving means andresponsive jointly to at least said first portion and said controlsignal to develop a resultant signal which is representative of at leastthe brightness of said image and whichincludes components inverselyrelated to said luminance effects developed by said undesiredcomponents, and means for utilizing said resultant signal and saidsubcarrier wave signal to reproduce said image, whereby said resultantsignal determines the brightness of said reproduction of said image andsimultaneously substantially reduces any brightness changes which saidsecond portion tends to produce therein.

6. A color-television system comprising: a transmitter including a firstsignal-translating channel having a plurality of amplifiers fordeveloping at least a first signal primarily representative of thevisual brightness of an image and substantially independent of itschromaticity, means for developing a subcarrier wave signal modulated byat least a signal which is primarily representative of the chromaticityof said image said modulated subcarrier wave signal including acomponent representative of the relative luminosity of elemental areasof the image, means for combining said developed signals to form acomposite signal, and means for transmitting said composite signal; anda receiver for said transmitted signals including a signal-translatingsystem for translating a first portion of said composite signalrepresentative of said first signal and for translating a second portionrepresentative of said modulated subcarrier wave signal, said secondportion tending to include undesired components affecting the visualbrightness in a reproduction of said image, including signal-derivingmeans coupledto said signal-translating system for deriving from saidsecond portion a control signal which is related to said componentrepresentative of said relative luminosity and which includes acomponent representative of the luminance effects developed by saidundesired components, a modulator device coupled to saidsignal-translating system and said signal-deriving means andresponsivejointly to at least said first portion and said control signal todevelop a resultant signal which is representative of at least thebrightness of said image said subcarrier wave `signaly to reproduce saidimage,

24 whereby lsaidresultant'signatdetermines the brightness of saidreproduction of said image and simultaneously substantially reduces anybrightness changes which Said second portion tendsV to produce therein.Y

7. A color-television system comprising: a transmitter including meansfor developing atleast a first signal primarily representative of thevisual brightness of an image and substantially independent of itschromaticity, means including a plurality of modulators, and an inversemodulator for developing a subcarrier wave signal modulated by at leasta signal which is primarily representative of the chromaticity ofsaidimage said modulated subcarrier wavel signal including a componentrepresentative ofthe relative luminosity of elemental areas of theimage, means for combining said developed signals to form a compositesignal, and means for transmitting said composite signal; and a receiverfor said transmitted signals including a signal-translating system fortranslating a first portion of said composite signal representative ofsaid first signal and for translating a second portion representative ofsaid modulatedv subcarrier wave signal, said second portion tending toinclude undesired components affecting the visual brightness in areproduction of Vsaid image, including signal-deriving means coupled tosaid signal-translating system for deriving from said second portion acontrol signal which is related to said cornponent representative ofsaid relative Vluminosity and which includes a component representativeof the luminance effects developed byrsaid undesired components, amodulator device coupled to said signal-translating system and saidsignal-deriving means and responsive jointly to at least said firstportion and said control signal to develop a resultant signal which isrepresentative of at least the brightness of said image and whichincludes components inversely related to said luminance effectsdeveloped by said undesired components, and means for utilizing saidresultant signal and said subcarrier wave signal to reproduce saidimage, whereby said resultant signal determines the brightness of saidreproduction of said image and simultaneously substantially reduces anybrightness changes which said second portion tends to produce therein. Y

8. In a color-television receiver, apparatus` for trans'- lating acomposite signal representative of an image in color and including afirst portion representative of the visual brightness of the image and asecond portion hav' ing a subcarrier wave signal modulated by at least asignal representative of the chromaticity of the image, the modulatedsubcarrier wave signal having a component representative of the relativeluminosity of elemental areas ofthe image, comprising: asignal-translating system responsive to said composite signal fortranslating at least said first portion and for translating a modulatedsignal which is representative of said modulated subcarrier wave signaland which includes undesired components tending to affect the visualbrightness of said image; signal-denving means coupled to said systemfor derivingl from said translated modulated signal a control signalwhich is related to said component representative of said relativeluminosity and which includes a component representative of the relativeluminosity effects developed by said undesired components; asignal-combining device coupled to said system and said signal-derivingmeans and responsive jointly to at least said first portion and saidcontrol signal to develop a resultant signal which is representative ofat least the brightness of said image and which includes componentsinversely related to said luminosity effects developed by said undesiredcomponents; and means for utilizing said resultant signal and saidsubcarner wave signal to reproduce said image, whereby said resultantsignal is representative of the brightness of said image withVanybrightness changes due to said undesired components being effectivelyeliminated.

9.V In a color-television receiver, apparatus for translating acomposite signal representative of an image in color andinclding a iirstportion representative'of the visual brightness of the image and asecond portion having a subcarrier Wave signal modulated by at least asignal representative of the chromaticity of the image, the modulatedsubcarrier wave signal having a component representative of the relativeluminosity of elemental areas of the image, comprising: asignal-translating system responsive to said composite signal fortranslating at least said rst portion and for translating a modulatedsignal which is representative of said modulated subcarrier Wave signaland which includes undesired components tending to alect the visualbrightness of said image; signal-deriving means coupled to said systemand including a signal generator and a detector for deriving from saidtranslated modulated signal a control signal which is related to saidcomponent representative of said relative luminosity and which includesa component representative of the relative luminosity eects developed bysaid undesired components; a signal-combining device coupled to saidsystem and said signal-deriving means and responsive jointly to at leastsaid first portion and said control signal to develop a resultant signalwhich is representative of at least the brightness of said image andwhich includes components inversely related to said luminosity eiectsdeveloped by said undesired components; and means for utilizing saidresultantV signal and said subcarrier wave signal to reproduce saidimage, whereby said resultant signal is representative of the brightnessof said image with any brightness changes due to said undesiredcomponents being eiectively eliminated.

l0. In a color-television receiver, apparatus for translating. acomposite signal representative of an image in color and including a rstportion representative of the visual brightness of the image and asecond portion having a subcarrier wave signal modulated by at least asignal representative ofV the chromaticity of the image, the modulatedsubcarrier wave signal having a component representative of the relativeluminosity of elemental areas of the image, comprising: asignal-translating system responsive to said composite signal fortranslating at least said first portion and for translating a modulatedsignal which is representative of said modulated subcarrier wave signaland which includes undesired components tending to aiect the visualbrightness of said image; signal-deriving means coupled to said systemand including a phase detector for deriving from vsaid translatedmodulated signal at a predetermined phase thereof a control signal whichis related to said component representative of said relative luminosityand which includes a component representative of the relative luminosityetects developed by said undesired components; a modulator devicecoupled to said system and said signal-deriving means and responsivejointly to at least said tirst portion and said control signal todevelop a resultant signal which is representative of at least thebrightness of said image and which includes components inversely relatedto said luminosity eiects developed by said undesired components; andmeans for utilizing said resultant signal and said subcarrier wavesignal to reproduce said image, whereby said resultant signal isrepresentative of the brightness of said image with any brightnesschanges due to said undesired components being eiectively eliminated. p'

11. In a color-television receiver, apparatus for translating acomposite signal representative of an image in color and including afirst portion representative ofthe visual brightness of the image and asecondV portion having a subcarrier wave signal modulated in bothamplirude and phase by signals representative of the chromaticity of theimage, the second portion having a component representative of therelative luminosityv of elemental areas of the image, comprising: alsignal-translating system responsive to said composite signal fortranslating at least said firstl portion and for translating aVmodulated `signal which is representative of said second portion andwhich includes undesired components tending to' affect the visualbrightness of said image; signal-deriving means coupled to said systemand including a signal generator arranged for developing a signalsynchronized in phase and frequency with said subcarrier wave signal, aphasedelay circuit and a synchronous detector coupled through said'phase-delay circuit to said generator for deriving from said translatedmodulated signal a control signal which is related to said componentrepresentative of said relative luminosity and which includes acomponent representative of the luminosity eiects developed by saidundesired components, said phase-'delay circuit having circuit elementsso proportioned as to delay the application of said developed signal tosaid Adetector by an amount related to the phase relationship of saidrelative luminosity component and one of said derived color componentsrepresentative of said chromaticity; a modulator device coupled to saidsystem and said signalderiving means and responsive jointly to at leastsaid rst portion and said control signal to develop a resultant signalwhich is representative of at least the brightness of said image andwhich includes components inversely related to said luminosity etectsdeveloped by said undesired components; and means for utilizing saidresultant signal and said subcarrier wave signal to reproduce saidimage, whereby said resultant signal is representative of the brightnessof said image with any brightness changes due to said undesiredcomponents being effectively eliminated.

12. In a color-television receiver, apparatus for translating acomposite signal representative of an image in color and including a rstportion representative of the visual brightness of the image and asecond portion having a subcarrier wave signal modulated by at least asignal representative of the chromaticity of the image, the modulatedsubcarrier Wave signal having a component representative of the relativeluminosity of elemental areas of the image, comprising: asignal-translating system responsive to said composite signal andincluding a first signal-translating channel for translating at leastsaidA first portion and a second signal-translating channel fortranslating a modulated signal which is representative of said modulatedsubcarrier wave signal and which includes undesired components tendingto aiect the visual brightness of said image; signal-deriving meanscoupled to said second signal-translating channel for deriving from saidtranslated modulated signal a control signal which is related to saidcomponent representative of said relative luminosity and which includesa component representative of the luminosity effects developed by saidundesired components; a modulator device coupled to said system and saidsignal-deriving means and responsive jointly to at least said rstportion and said control signal to develop a resultant signal which isrepresentative of at least the brightness of said image and whichincludes components inversely related to said luminosity etfectsdeveloped by said undesired components; and means for untilizng saidresultant signal and said subcarrier wave signal to reproduce saidimage, whereby said resultant signal determines the brightness of saidimage and simultaneously substantially reduces any brightness changeswhich said second portion tends to produce.

13. In a color-television receiver, apparatus for translating acomposite signal representative of an image in color and including afirst portion representative of the visual brightness of the image and asecond portion having a subcarrier wave signal modulated by at least asignal representative of the chromaticity of the image, the modulatedsubcarrier wave signal having a component representative of the relativeluminosity of elemental areas lof the image,vcomprising: asignal-translating system translatingza modulated signalof`predetermined band .width and composition which is representative ofsaid modulated subcarrier wave signal and which includes undesiredcomponents tending-to affect the visual brightness `of said image;signal-deriving means coupled to said second signal-translating channelfor deriving from said translated modulated signal a control signalwhich is related' to said component representative of said relativeluminosity and which includes a component representative of thelluminosity effects developed by said undesired components; a modulatordevicecoupled to said system and said signal-derivingmeans andresponsive jointlyto `at least said tirst portion and said controlsignal'to develop a resultant signal which is representative ofat leastthe brightness of said image and which includesv components inverselyrelated to said luminosity effects developed by said undesiredcomponents; and means for utilizing saidresultant signal and saidsubcarrier 'wave signal to reproduce said image, whereby said resultantsignal determines the brightness of said image and simultaneouslysubstantially reduces any brightness changes which said second portiontends to produce. n

v14.' In a color-television receiver, apparatus for translating acomposite signal representative of an image in colorand including a rstportion representative of the -visual brightness of the image and asecond portion having a subcarrier wave signal modulated by at least asignal representative of the chromaticity of the image, the modulatedsubcarrier wave signal having a component representative of' therelative luminosity of elemental areas of the image, comprising: asignal-translating systemA responsive to said composite signal fortranslating aty ieastsaid rst portion and for translating a modulatedsignal which is representative of said modulated sub- -carrier wavesignal and which includes undesired components tending to affect thevisual brightness of said image; signal-deriving means coupled to saidsystem for der'iving from said translated modulated signal a control1signal which is related to said component representative of saidrelative luminosity and which includes acomponent representative of theluminosity etects developed by said undesired components; a device forinversely modulating one signal by another coupled to said system andsaid signal-deriving means and responsive jointly to at least said firstportion and said control signal to develop a resultant signal which isrepresentative of at least the brightness of said image and whichincludes components inversely related to said luminosity electsdevelopedby said undesired components; and means for utilizing, saidresultant signal and said subcarrier wave signal to reproduce saidimage, whereby said resultant i signal is representative of thebrightness of said image with any brightness changes due to saidundesired components being etectively eliminated.

ing a subcarrierwave signal modulated by at least a signalrepresentative of the chromaticity of the image, the modulatedsubcarrier wave signal having a component representative kofthelrelative luminosity of elemental areas of lthe image, comprising: asignal-translating system responsive to said composite signal andincluding a tirst signal-translating channel for translating kat leastsaid iirst portion and asecond signal-translating channel fortranslating a modulatedv signal which is representative of saidmodulated subcarrier wave signal and which includes undesired componentstending to aiect the visual brightness of said image; signal-derivingmeans coupled to said'system for deriving from said translated modulatedsignal acontrol signal which is related to said component representativeof said relative luminosityv and which includes a componentrepresentativev of the luminosity ef- 28 vtoets-developed by saidundesired components; a-device for inversely modulating one signalbyanother coupled to said signal-translating channel and saidsignal-deriving means and responsive jointly to at least said firstportion and said control signal to develop a resultant signal which y isrepresentative `of at least the brightness of said image and whichincludes components inversely related to said luminosity effectsdeveloped by said undesired compo nents; and-means for utilizing saidresultant signal and said subcarrier wave signal to reproduce saidimage, whereby said resultant signal is representative of the brightnessof said image with anyY brightness changes due to said undesiredcomponents being eiectively eliminated.

16. In a color-television receiver, apparatus for translating acomposite signal representative of an image in color and Vincluding arst portion representative of the visual brightness of the image and asecond portion having a subcarrier wave signal modulatedby ,at least asignal representative of the chromaticity of the image, the modulatedsubcarrier wave signal having a component representative of the relativeluminosity of elemental areas of the image, comprising: asignal-translating system responsive to said composite signal includinga lter network having a substantially uniform frequency-responsecharacteristic for translating at least said irst portion and anotheriilter network having a substantially nonuniform frequency-responsecharacteristic for translating at least a modulated signal which isrepresentative of said modulated subcarrier wave signaland whichincludes undesired components tending to aect the visual brightness ofsaid image; signal-deriving means coupled to said system for derivingfrom said translated modulated signal a control signal which is relatedto said component representative of said `relative luminosity and whichincludes a `component representative of the luminosity etects developedby said undesired components; a modulator device coupled to said systemand said signal-deriving means and responsive-jointly. to at least saidrst portion and-said control signal to develop a resultant signal whichis representative of Vat least the brightness of said image and which'includes components inversely related to said luminosity eiectsdeveloped by said undesired components; and means for utilizing saidresultant signal and said subcarrier. wave signal to reproduce saidimage, whereby said resultant signal is representative of the brightnessof said image with any.

brightness changesdue to said undesired components being eiectivelyeliminated.

17. In a color-television receiver, apparatus for translating acomposite signal representative Vof an image in color and including airst portion representative of the visual brightness of the image and asecond portion having a subcarrier wave signal modulated by at least asignal representative of the chromaticity of the image, the modulatedsubcarrier wave signal having a component representative of the relativeluminosity of elemental areas of the image, comprising: asignal-translating system responsive to said composite signal fortranslating at least said first portion and for translating a modulatedsignal which is representative of said modulated subcarrier wave signalandwhich includes undesired cornponents tending to affect the visualbrightness of said image; signal-deriving means coupled to said systemfor deriving from said translated modulated signal a control signalwhich is related to said component representative of said relativeluminosity and which Vincludes a component representative of theluminosity effects developed by said undesired components; Ya modulatordevice including a pair of ampliers and a filter network coupled to saidsystem and said signal-deriving means and responsive jointlyto at leastsaid rst portion andapredetermined frequency portion vof said controlsignal-,to control ythe gain of said ampliiiers to develop a-resultantsignal which is representative of at least the .brightness 'of saidimage and which'includes 'componentsiinversely avvenne related to saidluminosity effects of said undesired components; and means for utilizingsaid resultant signal and said subcarrier wave signal to reproduce saidimage,

whereby said resultant signal is representative of the brightness ofsaid image with any brightness changes due to said undesired componentsbeing eiectively eliminated.

18. In a color-television receiver including -a color image-reproducingdevice having a plurality of control characteristics at least one ofwhich affects the visual brightness of a reproduced image and at leastanother of which atfects the chromaticity and the visual brightness ofthe reproduced image, an apparatus for translating a composite signalrepresentative of an image in color and including a rst portionrepresentative of the visual brightness of the image and a secondportion having a subcarrier wave signal modulated by at least a signalrepresentative of the chromaticity of the image, the modulatedsubcarrier wave signal having a component representative of the relativeluminosity of elemental yareas of the image comprising: asignal-translating system responsive to said composite signal fortranslating at least said lirst portion and for translating a modulatedsignal which'is representative of said modulated subcarrier wave signaland which includes undesired components tending to affect the visualbrightness of said V'image; signal-deriving means coupled to said systemfor deriving from said translated modulated signal a control signalwhich is related to said component representative of said relativeluminosity and which includes a component representative of theluminance elects developed by said undesired components; asignal-combining device coupled to said system and said signal-derivingmeans and responsive jointly to at least said rst portion and saidcontrol signal to develop a resultant signal which is representative ofat least the brightness of said image and which includes componentsinversely related to said luminance eiects of said undesired componentsfor application to said control characteristics; and means for applyingsaid resultant signal and said subcarrier wave signal to saidimage-reproducing device to reproduce said image, whereby said onecontrol characteristic controls the brightness of said image andsimultaneously substantially reduces any brightness changes which saidsecond control characteristic tends to produce.

19. In a color-television receiver, apparatus for translating acomposite signal representative of an image in color and including a rstportion representative of the brightness of the image and a secondportion having a subcarrier wave signal modulated by at least a signalrepresentative of the chromaticity of the image, the modulatedsubcarrier wave signal having a component representative of the relativeluminosity of elemental areas of the image, comprising: a rstsignal-translating channel responsive to said composite signal fortranslating at least a first signal representative of said lirstportion; a second signal-translating channel including a filternetwork'having a nonuniform frequency-response characteristic responsiveto said composite signal for translating at least a second signalrepresentative of said modulated subcarrier wave signal and whichincludes undesired color components tending to affect the brightness ofsaid image; a low-pass filter network responsive to said compositesignal for translating a component signal which is primarilyrepresentative of the low-frequency components of said tirst portion andhaving an output circuit; signalderiving means including a signalgenerator for developing a signal, a phase-delay circuit for delayingsaid signal developed in said generator, a detector coupled to saidnonuniform lter network and said phase-delay circuit for utilizing saiddelayed signal to eiect the derivation from said second signal of asignal representative of said relative luminosity component and whichincludes a component representative of the luminance c tects developedby` said undesired components; a irst amplifier circuit coupled to saiddetector andto said output circuit of said low-pass filter network fortranslating and for lcombining said derived signal and said componentsignal to develop a control signal; and a second amplifier having aninput circuit coupled to said first channel and said output circuit ofsaid low-pass filter network responsive jointly to said rst signal andsaid control signal to develop a resultant signal which isrepresentative of at least the brightness of said image and whichincludes components inversely related to said luminance eiects of saidundesired components, whereby said resultant signal is representative ofthe brightness of said image with any brightness changes due to saidundesired components being effectively eliminated.

20. In a color-television receiver, apparatus for translating acomposite signal representative of an image in color and including afirst portion representative -of the brightness of the image and asecond portion having a subcarrier wave signal modulated by at least asignal representative of the chromaticity of the image, the modulatedsubcarrier Wave signal having a -component .representative of therelative luminosity of elemental areas or the image, comprising: a rstsignal-translating channel responsive to said composite signal fortranslating at least a first signal representative of said tirstportion;

. a second signal-translating channel including a 0-4 megacycle lternetwork having a nonuniform frequencyresponse characteristic responsiveto said composite signal for translating at least a second signalrepresentative of said modulated subcarrier wave signal and whichincludes undesired color components tending to affect the brightness ofsaid image; a 0-2 megacycle lter network responsive to said compositesignal for translating a component signal which is primarilyrepresentative of the low-frequency components of said lirst portion andhaving an output circuit; signal-deriving means including a signalgenerator for developing a signal, a phase-delay circuit for delayingsaid signal developed in said generator, a detector -coupled to saidnonuniform filter network and said phasedelay circuit for utilizing saiddelayed signal to eiect the derivation from said second signal of asignal representai tive of said relative luminosity component; a firstamplitier circuit coupled to said detector and to said output circuit ofsaid 0-2 megacycle filter network for translating and for combining saidderived signal and said component signal to develop a control signal;and a second amplilier having an input circuit coupled to said firstchannel and said output circuit of said 0-2 megacycle iilter networkresponsive jointly to said rst signal and said control signal to developa resultant signal which is representative of at least the brightness ofsaid image and which includes components inversely related to saidundesired components, whereby said resultant signal is representative ofthe brightness of said image with any brightness changes due to saidundesired components being electively eliminated.

21. In a color-television receiver, apparatus for translating acomposite signal representative of an image in color and including airst portion representative of the brightness of the image and a secondportion having'a subcarrier wave signal modulated by at least a signalrepresentative of the chromaticity of the image, the modulatedsubcarrier wave signal having a component cumulatively representative ofthe relative luminosity attributable to the incremental color and thewhite of elemental areas of the image, comprising: a firstsignal-translating channel responsive to said composite signal fortranslating at least a first signal representative of said firstportion; a second signal-translating channel including a first band-passlter network responsive to said composite signal for translating apredetermined band width thereof, a device for inversely modulating onesignal by another for ond signal representative of said modulatedsubcarrier wave signal and which includes undesired color com- 31ponentstending to affect the brightness of said image and including asecond band-pass lter network for translating a predetermined band widthof said second signal; a lowpass lter network 'responsive to saidcomposite signal for translating a component signal which is primarilyrepresentative of the low-frequency components of said first portion andhaving an output circuit coupled to said device for inverselymodulating; said last-mentioned device being arranged to combine thesignal translated through said` rst band-pass lter network and saidcomponent signal to develop said second signal; signal-deriving meansincluding a signal generator for developing a signal, a phase-delaycircuit for delaying said signal developed in said generator, a detectorcoupled to said second bandpass filter network and said, phase-delaycircuit for utilizing'said delayed signal to effect the derivation fromsaid second signal of a color luminance signal representative of thatportion of said luminosity component attributable to said incrementalcolor and which includes a component representative of the brightnesseiects developed by said undesired color components, said meansincluding a source of a signal representative of the relative luminosityfor white and means for combining said signal representative of therelative luminosity for White and said color luminance signal to developa control signal; and another device for inversely modulating one signalby another coupled to said combining means and said 'iirstsignal-translating channel and responsive jointly to at least said firstsignal and said control signal to develop a resultant signal which isrepresentative of at least the brightness of said image and whichincludes components inversely related to said undesired components,whereby said resultant signal is representative of the brightness ofsaid image with any brightness changes due to said undesired componentsbeing effectively eliminated.

22. In a color-television receiver, apparatus for translating acomposite signal representative of an image in color and including aiirst portion representative of the brightness of the image and a secondportion having a subcarrier wave signal modulated by at least a signalrepresentative of the chromaticity of the image, the modulatedsubcarrier wave signal having a component cumulatively representative ofthe relative luminosity attributable to the incremental color and theWhite of elemental areas of the image, comprising: a firstsignal-translating channel including a -4 megacycle filter networkresponsive to said composite signal for translating at least a firstsignal representative of said rst portion; a second signal-translatingchannel including a first 2-4 megacycle lter network responsive to saidcomposite signal for translating a 2-4 megacycle portionthereof, adevice for inversely modulating one signal by another for deriving fromsaid 2-4 megacycle portion a second signal representative ofrsaidmodulated subcarrier wave signal and Awhich includes undesired colorcomponents tending to affect the brightness of said image and includinga second 2-4 megacycle filter network for translating the 2-4 mega--cycle portion of said second signal; a low-pass lter network responsiveto said composite signal for translating a component `signal which isprimarily representative of the 0-2 inegacycle components of said firstportion and having an output circuitV coupled to ksaid device forinversely modulating; said last-mentioned device being arranged todivide the signal translated through said tirst filter network by saidcomponent signal to develop said secondv signal; `signal-deriving means.including a signal gent erator for developing a signal, a'phase-delaycircuit for delaying saidl signal developedin said generator,-a de- Ytector coupled to said second lter network and said'phasedelaycircuitvfoi' utilizing said delayedsignal to effect the derivation fromsaid second signal of a color luminance signal representative of vthatportion of said luminosity .i component attributable to ksaidincremental color and Which'includes a component representative yof thebrightamaai ness effects developed by said undesiredvcolor components,said means including a source oftajsignal representative of' Vtherelative luminosity for white and means forrcombim'n'ginversely relatedto said undesired components, whereby said resultant signal isrepresentative of the brightnessofV said image with any brightnesschanges due to'said undesired components being efiectively eliminated.

23. in a color-television superheterodyne receiver, vapy paratus fortranslating a composite signalrepresentativeof an image in color andincluding a firstportionr repre'- sentative or" the brightness oftheima'ge and asecond portion representative ofA thechromaticityoftheimagefthe second portion having a componentrepresentative of the relative luminosity or elemental areas of. the'iniage,

comprising: an intermediate-frequency ampliiier circuit` responsive tosaid composite signal for translating at leastl said rst portion andyfor translating a signal which is representative of said second portionand which includes undesired components tending to aiect thebrightnessof "i t. said image; a low-pass filter network responsive to alowfrequency portion of said composite signal for-translating acomponent signal which is primarilyrepresentative of the low-frequencycomponents of said first portion and having an output circuit;signal-deriving, means including a signal .generator for developing asignal, a phase-delay circuit for delaying said signal developed.insaidgenerator, a detector coupled to said amplifier circuitand saidphase-delay circuit for utilizing said delayed signal to eect thederivation yfrom said secondV signal of a signal representative ofsaidtrelative luminosity component; and a second amplifier circuitcoupledto said intermediatefrequency amplifier `circuit,'to said`detector Vand to said output circuit of said low-pass filter network fortranslatingsaid first and secondv portions andy vsaidderived signais andresponsive jointly to said translated derived signals and said componentsignal to develop a control signal for controlling theV gain of saidamplifier, said first and second portions vbeing translated with saidcontrol'signal Y to develop a resultant signal which is representativeof at least the brightness 4of said image and which includesk componentsinversely relatedY to saidundesired compo-` nents, whereby saidresultant signal is representative of the brightness of said-image with,any brightnesschanges due to `said undesired components beingeiectivelyeliminated. Y Y

24. In a color-television superheterodyne receiver, apparatus fortranslating a composite signal representative -of an image in color andincluding a first portion representative of the brightness of the imageand a second portionV representative of the chromaticity of the image,the second portion having a component representative of the relativeluminosity of elemental areas of the image, comprising: anintermediate-frequency ampliier circuit responsive to said compositesignal for translating at least said rst portion and for translating -asignal which is representativetot'said second portion andwhich includesundesired components tending-to affect the brightness of said image; alow-pass filter network responsive toa 0-2' niegacycle portion of saidcomposite signal for translating a componentV signal which is primarilyrepresentative of the low-frequency components of said rst portion andhaving an output circuit; signal-deriving means including a signalgenerator for developing a signal, a phase-delay circuit for delayingsaid signal developed in said generator, a detector coupled to saidampliiier circuit and said phase-delay circuit for utilizing saiddelayed signal to etiect thederivation from said ysecond signal of asig-

